1. Field of the Invention
This invention relates to control systems for gas-fired burners in fireplaces and, more particularly, to a system wherein the supply of gas to a fireplace burner can be controlled by manipulation of a damper. The system of the invention is preferably used with fireplaces having a pilot valve lighting system.
2. Description of Related Art
The use of dampers in the vents or stacks of gas-fired furnaces is well known. When a burner is lighted in a furnace, the vent or stack must be open to allow the escape of noxious or lethal fumes produced as combustion byproducts. When a burner is not lighted, however, an open vent or stack allows heat to escape unless a damper is positioned so as to effectively block warm air from rising through it.
Various systems are disclosed in the prior art that are said to be useful for controlling the operation of a furnace damper so that the damper is open when the burner is lighted and closed when the burner is unlighted. Such systems are disclosed, for example, in U. S. Pat. Nos. 4,084,743; 4,087,045; 4,175,695; 4,294,226; 4,416,611 and 4,570,847. U.S. Pat. Nos. 4,084,743, 4,087,045 and 4,570,847 disclose motor operated systems for opening and closing furnace dampers. U.S. Pat. No. 4,175,695 discloses the use of a bimetallic strip in combination with two mercury switches, and U.S. Pat. No. 4,294,226 discloses a thermally actuated control system utilizing a fluid reservoir and piston. U.S. Pat. No. 4,416,611 discloses a system utilizing a thermostat, a solenoid coupled by a spring to a damper control lever, a manual override lever also connected to the damper control lever, a first switch that opens a fuel control valve in response to opening of the damper, and a second switch in parallel with the first switch that is actuated by operation of the manual override lever.
Although many complex systems have been disclosed for use in controlling damper operation in furnaces, most fireplaces with gas-fired burners still rely on manual damper controls. Failure to open a damper when the burner is lighted can cause smoke damage within a residence or business and can be dangerous to the user because of the noxious or toxic gases produced by the fire. Also, because conventional manual damper control levers are often located in the upper portion of the firebox, handling them after the burner is lighted, or soon after the burner is extinguished, can cause burns to the hands and arms of the user. One remote fireplace damper control utilizing a lever assembly accessible outside the firebox is disclosed, for example, in U.S. Pat. No. 4,264,217.
More recently, gas fireplaces have been marketed with pilot valves and burner lighting systems that can be actuated from a switch located on the front of the firebox or, remotely, from a wall switch. Damper control levers have been moved to the front of the firebox, where they are more easily accessible to the user without risk of injury. A need remains, however, for a fireplace gas control system with which the gas burner can be lighted and extinguished simply by manipulating a damper control lever disposed at the front of the firebox between its open and closed positions, respectively. Such a system is disclosed herein.
The damper-controlled gas system of the invention is preferred for use with gas fireplaces having gas valves with pilot lights that remain burning whether or not the damper is opened. The subject system preferably comprises a rotatable damper mounted inside the chimney vent pipe that is controlled by a transverse rod connected to a lever positioned so as to be conveniently accessible to the user.
According to one particularly preferred embodiment of the invention, the damper control lever hangs down from the top front of the firebox, where it can be manipulated to the left or right to open or close the damper as desired. Manipulation of the damper control lever in either direction causes the transverse rod to rotate the damper inside the chimney, and the rotation of the rod is desirably biased by a spring that is stretched in the over-center position and relaxes when the lever is pushed past the center to either side. A wire linkage preferably connects the damper control lever to a damper switch located outside the firebox so that a translational movement of the damper control lever to either the open or closed position causes the switch to close or open, respectively. A micro-switch is preferred for use in this application because of its smooth operation and reliability. When the damper control lever is in a position where the damper is closed, the open damper switch interrupts the circuit controlling a solenoid valve supplying gas to the main fireplace burner tube. Conversely, when the damper control lever is shifted to a position where the damper is open, the damper switch closes, completing the circuit that allows the solenoid valve to supply gas to the main burner tube, where it is ignited by the pilot light. Unless the damper switch is in the closed position, which can only occur when the damper control lever is positioned so as to open the damper in the fireplace vent, the main fireplace burner cannot receive gas through the solenoid valve, and cannot be lighted.
The present invention therefore provides a simple but reliable positive interlock between the fireplace damper and burner operation that cannot be accidentally forgotten during use, preventing damage to premises or physical injury to users or occupants that might otherwise occur.